1. Field of the Invention
The present invention relates to radio IC devices, and particularly to a radio IC device including a radio IC used for an RFID (Radio Frequency Identification) system.
2. Description of the Related Art
A RFID system has been developed for commodity management in recent years. In the RFID system, information is transmitted by non-contact communication between a reader/writer that generates an induction field and an IC chip (may be referred to as IC tag or radio IC chip) which stores commodity information and other information attached on the package or other item of the commodity.
Japanese Unexamined Patent Application Publication No. 2002-232221 discloses a transmitter/receiver unit including an IC chip-including radio IC device together with other chip components. In the transmitter/receiver unit, a circuit board on which the IC chip is mounted is enclosed in a shielding case, and an antenna element is further disposed on the circuit board.
However, since the antenna element is disposed as an independent component different from the radio IC chip within the shielding case, the radio IC device is relatively large and, consequently, the size of the transmitter/receiver unit is increased. In order to avoid the increase in size, the antenna element is miniaturized. However, this reduces the radiation characteristics of the antenna element, which causes problems, such as a decrease in communication distance.